1. Field of the Invention
The invention relates to a scanning system and method based on the principle of confocal microscopy.
2. The Prior Art
Such scanning systems are used for scanning an object and for enabling both scanning of a point along an axis (two-dimensional scanning) and scanning of a surface disposed about an axis (three-dimensional scanning). Thus, such a device is suitable for a point sensor and a flat panel sensor.
The basic principles of confocal 3D scanning are known. The determination of the altitude of a point on an object is achieved in the prior art by determining, for each point of a drilled board constituting an aperture array, that position of the object, relative to the imaging optics or the entire scanning device, at which the greatest amount of light travels back through the drilled board. In addition, during the movement of the object relative to the imaging optics, a plurality of image frames is recorded and for each dot in the image that frame in the frame sequence is determined in which the intensity is greatest. The vertical profile of the object can be determined from the knowledge of the position of the image frame within the frame sequence. However, typically frame sequences of some 10 to 100 frames must be recorded, so that the measuring procedure, using current recording technologies, takes several seconds or even longer. To shorten the total measurement time to one acceptable for intraoral dental imaging, considered to be approximately 200 ms, it is necessary to use extremely complex video technology and data evaluation, or to lose accuracy in at least one of the three dimensions. Moreover, high demands are made on the mechanics for producing the relative motion between the object and the imaging optics.
In the prior art, it is known that a rapid change in the distance between an object and the imaging optics can be achieved by inserting an element made of a medium which has a different optical density and a variable thickness, and is moved in such a way that the effective thickness is varied over time. A suitable medium for this purpose is glass, for example.
Furthermore, 3D scanning techniques used in an intraoral camera for scanning teeth are also known, which work on the principle of phase shift triangulation.
Moreover, the use of point sensors or line sensors is well known in current 3D scanning procedures, the 3D-object being moved relatively to the sensor during the measuring operation, which is often referred to as scanning.